REEF CHARACTERIZATION AND CORAL IDENTIFICATION IN A UNIT OF THE LARES LIMESTONE (LATE OLIGOCENE) EXPOSED IN ROAD PR-111, BETWEEN SALTO COLLAZO AND THE INTERSECTION WITH ROAD PR # 445

Reef characterization has been made in one unit of the Lares Limestone of Oligocene age in north Puerto Rico. This unit is part of the 4^th parasecuence of nine proposed by Ortega (2009) in the Lares Limestone. The unit is exposed laterally for 120m in road PR-111. Preliminary data indicates that this unit represents patch reef facies that extends for 30 meters laterally, were 4 main facies were identified: 1) finger coral facies, 2) head coral facies, 3) platy coral facies, and 4) calcareous silt. The Finger coral facies are in-situ corals predominated by Pocillopora guantanamensis and Porites portoricensis. This facies also include isolated mounds of head corals. Finger coral is the major frame builder of the patch reef. The head coral facies is predominated by in-situ corals of Solenastrea bourbonni, Montastrea cannalis, Stylophora sp., Goniopora imperatoris, Goniopora hilli, Goniastrea canalis, and Stephanocoenia sp., with occurrence of encrusting algae in some areas. The calcareous silt facies contains fragments of red algae, oysters and bivalves, with isolated head corals. This facies is often intercalated with the finger coral facies. This unit changes laterally to a calcareous shale with occasional patches of the finger coral facies and isolated mounds of head corals. This research helps understand better the Lares Limestone in terms of lateral facies changes and parasequences. Also, this research aids to understand the coral reef development in the late Oligocene in Puerto Rico.